Musnad Ahmad

Amr bin Kathir says: I said to Abdur Rahman bin Kaysan, "Why do you not narrate to me any hadith from your father?" He replied, "When did you ever ask me for it?" Then he said, "My father told me that he once saw the Prophet (peace be upon him) coming out of the kitchen and reaching the well. At that time, he was only wearing a lower garment; the upper sheet was not on his blessed body. Near the well, he saw some slaves performing prayer. He untied the knot of his lower garment, sprinkled water, and performed two rak'ahs. However, I do not remember whether it was the Zuhr prayer or the Asr prayer."

Abdur Rahman bin Kaysan says that I asked my father Kaysan how he found the Prophet (peace be upon him). He replied, "Once I saw the Prophet (peace be upon him) wrapped in a cloth, praying either Zuhr or Asr at the elevated well called Bir bin Muti'. At that time, he prayed two rak'ahs."